1. Field of the Invention
This invention relates to a gasification monitor, a method for detecting mist, a film forming method and a film forming apparatus, which are applicable to a technique where, for example, a liquid material or a solid material is vaporized and supplied into a chamber to perform a designated processing, such as chemical vapor deposition (CVD).
2. Background Art
In order to manufacture a desired semiconductor device, generally, there are repeatedly carried out a film deposition process and a pattern etching process against a semiconductor wafer. With high integration and high-density of semiconductor devices, the specifications of deposition technique are becoming increasingly severe every year. For instance, even for an oxidation film of great thinness (e.g. insulation film, gate insulation film, etc. of a capacitor in a device), an electrode film and a wiring film, it is required to reduce the film-thickness of these films furthermore. Giving an example of a gate insulation film, a method for forming HfO2-film, ZrO2-film, SiO2-film by MOCVD (Metal Organic Chemical Vapor Deposition) method is proposed. In the above method, organic metallic compounds, such as Hf(OtBu)4, Zr(OtBu)4 and SiH(NMe2)3, are used as deposition materials. However, it should be noted that all of these materials are liquids at ambient temperatures and have respective vapor pressures of relative lowness at temperatures less than their resolving temperatures. Therefore, Japanese Unexamined Patent Publication (kokai) No. 2001-148347 discloses a method where these materials are vaporized in a vaporizer and continuously, the resultant vapor is introduced, as a processing gas, into a deposition chamber for film deposition due to the thermal decomposition of the vapor.
In the MOCVD method mentioned above, there is a worry that if the evaporation of liquid material is incomplete in the vaporizer, the liquid material in the form of mist in a processing gas is transported the chamber, so that the liquid materials may adhere to a thin film on a substrate.
Meanwhile, the vaporizer disclosed in the above publication (kokai) No. 2001-148347 is provided with a variety of ingenious plans in order to perform its vaporization effectively. Nevertheless, the same publication (kokai) No. 2001-148347 does not make arrangements to detect the mist included in the processing gas to be supplied into the chamber. Thus, it is impossible to detect deposition defects due to the mist unless a thin film has been deposited on a substrate practically.
Additionally, since it takes a long time to inspect defects after the deposition, it is difficult to take prompt measures to meet the situation, causing the productivity of a deposition process to be lowered.